University of Delaware shark scientists faced that question after a large sand tiger shark completely swallowed a smooth dogfish (Mustelus canis). The three-foot dogfish, a type of shark, had itself devoured the menhaden (Brevoortia sp.) bait fish that the researchers had placed on a fishing line.

The marine version of matryoshka dolls happened while researchers attempted to recapture sharks that they had previously tagged with radio transmitters in Delaware Bay. The University of Delaware’s Ocean Exploration, Remote Sensing, Biogeography Lab tags and tracks the tiger sharks to improve human understanding of shark migration. Sharks face intense threats to survival worldwide and documenting shark movements may improve conservation efforts.